Laying a cable in a tube according to this latter technique generally takes place by injecting a fluid into the tube, the fluid being injected at a speed higher than the laying speed of the cable, mechanical means arranged upstream of the fluid injection being provided for pushing the cable inside the tube. It is common to lay cables using this technique, especially very long optical fibre cables.
However, this technique suffers from a drawback resulting from the required space and the mass of the device including means allowing injection of the carrier fluid as well as means for pushing. This drawback is especially obvious during laying where the introduction site of the cable is located in a confined space or when the tube end, able to receive the cable, terminates very close to a side wall of the introduction chamber, or during laying of small-diameter optical fibre cables and relatively fragile cables.
The device described in document U.S. Pat. No. 5,749,565 describes such a device especially unsuited to laying when the tube which should receive the optical fibre is close to the left wall of the introduction chamber.